serial: imx: TX DMA: clean up sg initialization

Inverting the logic of the if statement for the sg initialization
makes the if statement easier and better to read.

No functional change.

Signed-off-by: Dirk Behme <dirk.behme@de.bosch.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/imx.c

@@ -539,15 +539,15 @@ static void imx_dma_tx(struct imx_port *sport)
 
  sport->tx_bytes = uart_circ_chars_pending(xmit);
 
- if (xmit->tail > xmit->head && xmit->head > 0) {
+ if (xmit->tail < xmit->head) {
+ sport->dma_tx_nents = 1;
+ sg_init_one(sgl, xmit->buf + xmit->tail, sport->tx_bytes);
+ } else {
  sport->dma_tx_nents = 2;
  sg_init_table(sgl, 2);
  sg_set_buf(sgl, xmit->buf + xmit->tail,
  UART_XMIT_SIZE - xmit->tail);
  sg_set_buf(sgl + 1, xmit->buf, xmit->head);
- } else {
- sport->dma_tx_nents = 1;
- sg_init_one(sgl, xmit->buf + xmit->tail, sport->tx_bytes);
  }
 
  ret = dma_map_sg(dev, sgl, sport->dma_tx_nents, DMA_TO_DEVICE);